Manhole lid clamp



Dec. 26, 1950 F, 1', DlxN 2,535,275

. MNHLE LID cLAMP Filed Jan. 28, 1946 Patented Dec. 26, 1950 UNITED STATES ATENT OFFICE 2 Claims.

This invention relates to man hole covers and is particularly concerned with releasable locking mechanism for retaining the cover in locked position with the manhole base.

As is known, man holes are openings to sewers or other underground passages and as at present constructed embody a metallic flanged cylindrical base at the mouth of the openingand which is normally covered by a lid or cover.

The covers as now generally in use are in the form of rather heavy discs having their margins resting on the base ange and the weight of the covers only, are relied upon to retain same in position.

The importance of covers for man holes cannot be overestimated as an unguarded open manhole presents a great danger to the public. While the usual manholecoverwill retain its position in closing the manhole under ordinary conditions, there s, however, a likelihood of same being dsplaced by ooded sewers or even by automotive wheels in the event that the cover has become warped. At any rate, a manhole cover loosely seated on a manhole base is subject to vibration by wheels passing over same with a resulting annoying noise.

It is accordingly a primary object of this invention to provide a manhole cover having mechanism assoc'ated therewith for locking the cover in position on a manhole base whereby the above noted objections are overcome.

In the provision of locking mechanism for retaining manhole covers in closing position on manhole bases, it is important that such locking mechanism be readily releasable for removing the covers and that the locking mechanism be so Constructed that the release thereof can be elected only by authorized persons in order to avoid unauthorized removal as by pranksters or the like.

It is accordingly a further object of the inn vention to provide a manhole cover having releasable locking mechanism carried thereby and which is eiective to lock the cover to a manhole base, and the locking mechanism being so constructed and so associated with the cover that it can be released only by special tools to be in the possession of persons authorized to remove the cover.

Other objects and advantages of the invention will become apparent in the course of the following detailed descripton, taken in connection with the accompanying drawing, wherein:

Fig. 1 is a top plan view of a manhole cover together with a fragment of a manhole base and showing the locking mechanism mainly in dotted lines beneath the cover.

Fig. 2 is a right side edge view of the cover with the locking mechanism as when the cover is removed from the base.

Fig. 3 is a vertical sectional View in the plane of line 3 3 on Fig. 1.

Fig. 4 is a top plan view of one of the latches included in the locking mechanism.

Fig. 5 is a left end view of the latch shown in Fig. 4.

Referring now in detail to the drawing, C designates the cover which may have any desired sure face conguration.

The cover C is provided on its under face with a housing Ill which is preferably integral with the cover and which is of generally semi-cylindrical form open at its opposite ends. The housi ing lil is preferably disposed centrally of the cover and is elongated with its axis in a diameter of the cover. I

The cover is further provided with a pair of stirrups or latch guides II defining openings alined with the opening in the housing and with the axes of the stirrup openings in the same diameter as above referred to. The cover C is further provided with a pair of rectangular apertures l2 also in said diameter of the cover, and the apertures are in .spaced relation with each thereof adjacent an end of the housing Ill.

A pair of latches I3 are provided and each lis of elongated form and is rectangular in cross section. Each latch is provided with a rectangular aperture lll of the same size as apertures I2. Each latch further includes a tongue I5 on one end thereof for engagement beneath the flange F of a manhole base B, and each latch further includes a circular head I 6.

The latches i3 are mounted as indicated more clearly in Fig. 3 wherein the body portions thereof slidably extend through the stirrups II and the heads I6 thereof are disposed within the housing HB adjacent the opposite ends thereof in the locked position of the cover.

A coil spring I'i is disposed within the housing l@ with its opposite ends bearing on the heads It of the two latches i3.

When the cover C is in its locked position of Fig. 3 the tongues I5 engage beneath the base ange F and the shoulders I5 above the tongues are forced against the cylindrical wall of the flange by the spring I'l. In the locked position the apertures I2 and lli while being in the same diameter of the cover are staggered, that is, lapertures I4 are further from the ends of housing I0 than are apertures I2, the apertures I2 and I4 however, overlapping as shown such that there is a through opening at each pair of apertures I2, I4.

The locking mechanism is released by use of a pair of tools T which in effect are wedges and in use the points thereof are inserted into both apertures of each pair I2, I4, and the wedges are then forcibly driven in for moving the latches I3 toward each other with a resulting compression of the spring I'I, and until the apertures are alined with the rectangular portions of the tools disposed therein. In this position of the latches the tongues I5 are Withdrawn from beneath the flange F, and the cover C can be lifted from its closing position.

When it is desired to restore the cover to closing position, it is laid on ange F, and then the tools T are knocked out of the apertures whereupon the spring I1 will automatically move the latches to cover locking position.

It is to be noted that While the latches I3 and spring II are free of each other, they will retain a symmetrical and operative position on the cover since the latches are outwardly movable to equal extents as governed by ange F, and the tools T draw the latches inwardly equal distances, and for this reason the latch heads I6 and spring I'I will always remain in the open ended housing I 0.

While I have disclosed my invention in accordance with a single specific embodiment thereof, such is to be considered as illustrative only, and not restrictive, the scope of the invention being defined in the subjoined claims.

What I claim and desire to secure by U. S. Letters Patent is:

1. In a structure of the character disclosed, a circular manhole cover provided with a pair of rectangular apertures in a diameter thereof and in spaced relation to the center thereof, a pair of alined elongated latches slidably supported by the cover on the underside thereof in said diameter and provided with locking tongues on their opposite ends, the adjacent ends of said latches being vin spaced relation and positioned between said apertures, a spring supported by said cover and disposed between said adjacent ends for forcing said latches apart to locking position, and a rectangular aperture in each latch of the same dimensions as the apertures in the cover, the latter apertures being normally displaced in said diameter relative to the rst apertures but lapping same whereby providing through openings for the insertion of the wedged tools for driving the latches toward each other against the action of said spring.

2. A structure according to claim l wherein said latches are slidably supported in stirrups depending from the under side of said cover, and wherein said spring and the adjacent ends of said latches are disposed in a housing depending from the under side of said cover and disposed between the rst named apertures.

FRANK THOMAS DIXON.

REFER-ENOES CITED The following references are oi record in the file of this patent:

UNITED STATES PATENTS Number Name Date 608,601 Henneberg et al. Aug. 9, 1898 907,085 McNutt Dec. 15, 1908 1,102,422 McKeon July 7, 1914 1,183,490 Pollgreen May 16, 1916 1,400,399 Yaeche Dec. 13, 1921 1,693,190 Benedetti Nov. 27, 1928 1,988,360 Moore Jan. 15, 1935 FOREIGN PATENTS Number Country Date 589 Great Britain of 1890 

